1. Field of the Invention
This invention relates to a magnetic bubble module and more particularly to a substrate provided in the module, for supporting magnetic bubble chips.
2. Description of the Prior Art
In a conventional magnetic bubble module, a thin film of, for example, polyimide is attached onto a substrate of, for example, bakelite and a plurality of magnetic bubble chips are arranged on the thin film of polyimide to form a chip plane. Such a plane or a plurality of such planes are housed in the casing-shaped structure of an X-direction and a Y-direction driving coils for generating a rotating magnetic field. The coil structure is surrounded by the frame of permanent magnets and yoke plates for creating a bias magnetic field.
With this configuration, the heat generated by the coils is dissipated through the upper and lower yokes and a heat sink of, for example, aluminum, but the part of heat generated by the internally disposed coil cannot be effectively dissipated. Consequently, the temperature of the magnetic bubble chips reaches 25.degree. C and above even when air-cooling is applied. If the ambient temperature around the magnetic bubble module is higher than 40.degree. C, it is impossible for the magnetic bubble chips to perform a stable memory operation. If heat is radiated by means of blast through the module, the module must include a superfluous space for blast ducts. Accordingly, the sizes of the coils must be increased and the power for driving them must also be increased.
Another method for dissipating heat is to use the thermal conduction phenomenon. In general, however, a material having a good thermal conductivity has also a good electrical conductivity and if a material having a good electrical conductivity is placed in a high-frequency coil, eddy current is induced in the material so the Q-value of the coil is reduced and the magnetic field within the coil is also disturbed. Consequently, this method is not practically used.